THE PKJEYALSKY HOE.SE. 



47 



to be peculiar to the skeleton of the donkey ; but it is also met 

 with in the horse, and is not now held to be a distinguishing 

 peculiarity of any particular race of horse. In the ass and its 

 hybrids, the number (five) is typical and constant. The first lum- 

 bar vertebra (Fig. 17) possesses a form intermediate between that of 



Fig. i6. — Eighteenth thoracic vertebra (lateral aspect). 



the domestic horse and that of the donkey. The anterior articular 

 process is pointed at the end, and in this respect resembles the 

 corresponding vertebra of the ass. In the horse, the process is 

 rounded and has a broader end. The spinous process in the 



Fig. 17. — Lumbar vertebra (caudal aspect) 



Prjevalsky horse is bounded by an even backwardly sloping line, 

 which is not convexly curved as in the ass. Of the remaining 

 lumbar vertebrae, the fourth and fifth have been injured and, 

 therefore, are not suitable for comparison. The second and third 

 show no outstanding peculiarities. These vertebrae were not 



